Bullying has been described as one of the most tractable risk factors for poor mental health and educational outcomes, yet there is a lack of evidence-based interventions for use in low and middle-income settings. We aimed to develop and assess the feasibility of an adolescent-led school intervention for reducing bullying among adolescents in Indonesian secondary schools. The intervention was developed in iterative stages: identifying promising interventions for the local context; formative participatory action research to contextualize proposed content and delivery; and finally two pilot studies to assess feasibility and acceptability in South Sulawesi and Central Java. The resulting intervention combines two key elements: 1) a student-driven design to influence students pro-social norms and behavior, and 2) a teacher-training component designed to enhance teacher's knowledge and self-efficacy for using positive discipline practices. In the first pilot study, we collected data from 2,075 students in a waitlist-controlled trial in four schools in South Sulawesi. The pilot study demonstrated good feasibility and acceptability of the intervention. We found reductions in bullying victimization and perpetration when using the Forms of Bullying Scale. In the second pilot study, we conducted a randomised waitlist controlled trial in eight schools in Central Java, involving a total of 5,517 students. The feasibility and acceptability were good. The quantitative findings were more mixed, with bullying perpetration and victimization increasing in both control and intervention schools. We have designed an intervention that is acceptable to various stakeholders, feasible to deliver, is designed to be scalable, and has a clear theory of change in which targeting adolescent social norms drives behavioral change. We observed mixed findings across different sites, indicating that further adaptation to context may be needed. A full-randomized controlled trial is required to examine effectiveness and cost-effectiveness of the program.